First, get your crumble together in a bowl. Mix flour, salt, and shortening with hands making the start of the crumble. Mix together so little ball-ish crumbles start to form. Add walnuts mix around again, then lastly add syrup bringing it all together. Set aside. Then heat oil in cast iron skillet on stove, then add remaining filling ingredients stirring occassionally. Cook on medium heat for 4-6 minutes until a fork will easily stick through the apples but not too soft. Do not over cook or you will end up with mush. Kind of think of it like cooking el dente pasta. Remove from heat, don’t forget to use an oven mit. Spread crumble evenly on top just using your fingers to spread around. Bake in oven at 375 for additional 5 minutes until crumble has started to slightly brown and apples are bubbling around side. Take out to cool 5 minutes and the crumble will be perfectly crisp. Eat while warm!!